Since rubber-reinforced resins represented by ABS resins have excellent workability, impact resistance, mechanical properties and chemical resistance, they are used in a wide range of fields including the field of vehicles and the field of household appliances as molding materials for various constituent parts. For the above various constituent parts, as a method for imparting luxury, durability and better feeling of touch, metal plating on the surface of the constituent parts has been employed. Particularly, molded articles of rubber-reinforced resins are noticed since they can be metal-plated on a surface thereof, and are widely used as metal-plated molded parts including door mirrors, radiator-grilles, knobs, housings and caps of cosmetic containers.
Recently, durability of metal-plated constituent parts is required, and a resin composition for metal plating which is more excellent in metal plating adhesion strength and chemical resistance than before is also required with expansion of application fields.
Conventionally, various methods have been attempted for improving metal plating adhesion strength of rubber-reinforced resins represented by ABS resins. For example, Patent Document 1 has proposed a method of blending predetermined amounts of a rubber-containing graft copolymer and two AS resins different in average molecular weight and content of vinyl cyanide monomers, the rubber-containing graft copolymer being obtained by polymerizing vinyl monomers in the presence of two diene-rubber polymers different in gel content and degree of swelling. Patent Document 2 has proposed a method in which a rubber-reinforced resin is adjusted to have specific ranges of content of rubbers, content of vinyl cyanide monomers in the acetone-soluble matter, Mw/Mn ratio in the acetone-soluble matter and Mz/Mn ratio in the acetone-soluble matters.
The method disclosed in Patent Document 1 requires use of two kinds of diene rubbers and two kinds of AS resins different in properties, and thus the process for producing the rubber-reinforced resin is complicated, and metal plating adhesion strength and chemical resistance are still insufficient for some applications such that further improvement is required. The method disclosed in Patent Document 2 is complicated due to processes for adjusting the Mw/Mn and Mz/Mn ratios of the acetone-soluble matter to specific ranges, and metal plating adhesion strength and chemical resistance are still insufficient for some applications such that further improvement is required. In addition, when metal-plated molded articles are used as battery cell casings for lithium ion rechargeable batteries, they are required to have chemical resistance because they contact an electrolyte solution, and are also required to prevent moisture from invading from the outside.
[Patent Document 1]: JP-A-2000-154291
[Patent Document 2]: JP-A-2002-256043